This exhibit is branded as being made by Hammond on the base cap with the Type designation and country of origin etched into the glass. The Hammond AO-14 M2 organ amplifier uses a pair of 7591 valves in the output stage.
We have data from Sylvania who describe the 7591 as a power output tube that is capable of 43 Watts of output at very low distortion when operated in push-pull and Class AB1. Or in Ultra linear configuration, an output of 32 Watts with a 400 Volt HT. RCA describe the 7591 as designed for high quality audio amplification.
The box anode - face view.
The Hammond AO-14 M2 amplifier. From an ebay listing.
